This is indeed an interesting idea, but tmckay makes a good point - how far can you really trust people you don't know in a true SHTF scenario? I'm not quite that cynical - I think people you know well will not screw you unless they have no other choice, but a well organized group who's planned and trained together will likely stick together in a crisis and not turn inward unless things are REALLY REALLY bad.

The problem is in finding people you can talk about SHTF honestly with, then choose a leader and leadership structure, then come up with a training plan, then finding the time to train. Much easier said than done.

I've thought for a long time there's a market for neighborhoods that are built with self-reliance / preppers in mind, then only sold to people of the right mindset and who agree to participate. They'd have to be screened, and agree via some kind of a contract to a certain amount of training and duties and prep for their families and the community. Then if SHTF you'd have defensible homes arranged in a defensible manner populated with people who are trained and equipped to protect themselves and survive for the long haul. Such a community is apt to be able to hold on indefinitely.